1. Field of the Invention
The present invention relates to a temperature control system for a semiconductor wafer or substrate (which will be referred to as "substrate" hereafter), and more particularly to a system which controls the temperature of a substrate to be processed in a vacuum processing apparatus such as a sputtering apparatus, CVD apparatus, etching apparatus, or the like, by heating or cooling the substrate being processed in response to any changes in the temperature thereof.
2. Description of the Prior Art
It is known that a substrate to be processed in a vacuum processing apparatus such as a sputtering apparatus, CDV apparatus, etching apparatus, or the like is heated or cooled so that it can be maintained at a constant temperature.
There are various known types of temperature control systems that have been used to heat or cool the substrate being processed in a vacuum. There are also other types of temperature control systems that blow temperature-controlled cooling or heating gases (inert gases such as Argon gases, for example) from behind the substrate being processed in a vacuum (as disclosed in Japanese Patent Publications (not examined) No. 58-132937 and No. 62-50462).
Those types of temperature control systems which blow temperature-controlled gases onto the back of the substrate are arranged as shown in FIGS. 7 and 8.
In one type of the temperature control system as shown in FIG. 7, a substrate 1 to be processed is firmly held by a chuck 3 onto its holder 2, and the holder 2 has an aperture 4 extending therethrough, facing opposite the substrate 1. Gas is blown through a gas delivery conduit 5 onto the back of the substrate 1. A resistance thermal unit 6 is provided outside the holder 2, which heats the gas flowing through the gas delivery conduit 5. Cooling occurs by circulating water or other coolants through a circulating conduit 8 which is provided on a flange 7.
In another type of the temperature control system as shown in FIG. 8, a substrate 1 to be processed is firmly held by a chuck 3 onto its holder 2, and gas is blown through a delivery conduit 5 onto the back of the substrate 1. Heat is provided by a sheathed heater 9, which is embedded in the holder 2, and cooling occurs by circulating coolant or other mediums through a circulating conduit 8 which is provided in the holder 2.
The systems, shown in FIGS. 7 and 8, have a common problem in that they do not respond quickly to any changes in the temperature. Therefore, no adequate temperature control is provided.
In the system shown in FIG. 7, the resistance thermal unit 6 is exposed to the atmosphere. This may cause a thermal loss by allowing an escape of its heat into the atmosphere. The unit 6 has a large inherent thermal capacity which also prevents the system from responding quickly whenever any change in temperature occurs when a substrate is being processed. Thus, heating or cooling cannot be provided in good time.
In the system shown in FIG. 8, which includes the sheathed heater 9 embedded in the holder 2, the escape of the heat into the atmosphere may be avoided, but the holder 2 must be large, and accordingly must possess a large inherent thermal capacity heater. This would also prevent the system from responding quickly to any changes in the temperature when a substrate is being processed, and heating or cooling cannot be provided in good time.
When a substrate is being processed by any process such as sputtering, a certain time loss must be allowed for until the substrate is heated or cooled to the desired temperature whenever any change in the temperature thereof occurs. This time loss causes a corresponding reduction in the processing efficiency. For example, whenever the temperature in the substrate is raised by the heat produced by sputtering, it is difficult to control the power output of the heater so that the substrate can be maintained at a constant temperature.